chi-square distribution's name history

[JeenLeen]

Why is the chi-square distribution called the "chi-square" distribution?

I know enough about how it's squaring an existent distribution, so the "square" makes sense, but why did they choose "chi"? Was it just arbitrarily choosing a Greek letter? (At one point I hoped it was the last name of a statistician, but kinda doubt it after a bit of study (aka, professors speaking of it & Wikipedia).)

[Thomas Cardew]

I believe it was just the notation Pearson used when he derived it. So arbitrary selection of a Greek letter as a random variable.

https://stats.stackexchange.com/ques...d-distribution

http://jeff560.tripod.com/c.html

[Jay R]

It came from Fisher's abbreviation for the exponent in a multivariate Normal distribution. He wrote -½ χ² instead of -½ x^T Σ^-1 x.